1. Field of the Invention
The present invention relates to movement of products such as hollow cast metal pipe between production stations.
2. Description of the Prior Art
In the production of objects such as elongate cast metal pipes, centrifugal casting has been commonly used. In such a casting operation, the pipe is cast in a cylindrical mold. Molten metal, such as iron, is fed into the mold through a trough. The trough has a spout at one end which is curved toward the sidewall of the mold. A sand core is inserted into the bell end of the mold to form the inside contour of the pipe bell. The mold is rotated and once it is brought up to the appropriate speed, molten metal is poured into the trough. Once the bell end of the pipe has formed, the mold is moved horizontally while rotating. The stream of molten metal discharged from the spout flows tangentially onto the surface of the mold, where it is held in place by centrifugal force. The molten metal forms a homogeneous pipe with a cylindrical bore. By controlling the pouring rate and movement of the mold, the wall thickness of the pipe produced can be held within desired tolerances.
After the pipe has been completely cast, the mold is kept rotating until the pipe has cooled to a desired temperature. The pipe must then be taken from the casting machine and transferred to a heat treating furnace. The pipe is then moved through the heat treating furnace and heated and cooled to produce the desired properties in the finished pipe.
Pipes of different diameters have been produced in this manner. For example, ductile iron pipes of 8, 12, 14, 16, 18, 20 and 24 inches are common. For some applications, it is desirable to produce pipe of larger diameter, such as diameters ranging from 30-48 inches.
It is desirable to maintain pipe diameter within manufacturing tolerances. In addition, it is desirable to produce pipes having wall thicknesses within manufacturing tolerances. Both of these constraints are problematic in the case of large diameter pipe having diameters ranging from 30-48 inches. Moving the pipe between the casting production station and the heat treating furnace station, as well as treatment within the heat treating furnace, can result in the pipe going out-of-round or in the wall thicknesses changing due to the weight of the cast metal and the effects of gravity.